Case studies
Profiting from managing soil PH
In Australia, there is a huge economic loss due to soil acidity and is researched to be many times higher than from dry land salinity (Commonwealth of Australia, 2001b). Researchers have proven that a scheduled liming program is an essential part of quality farming practices where soils are acid or acidifying.
When lime is not regularly applied to acidifying soils, productivity can decline dramatically over time – often unnoticed. Rehabilitation of acid soils takes time and frequent applications of lime.
Maintaining soil pH by regular application of maintenance levels of lime will avoid the need for expensive and slow remediation management, with data from Primary Industries and Resources South Australia (PIRSA) showing an investment in lime on cropping land likely to return $3 for each $1 invested.
Some case studies are given below of how land managers have tackled soil acidity.
Case study 1
Economic returns from monitoring and remediation of acid soils with lime application
A long term soil acidity monitoring study was conducted in the Gabby Quoi Quoi catchment located in the central agricultural region of Western Australia, measuring change in soil pH at GIS located sample points in 1999 and 2006.
Of the 300 sites sampled, 75% of the topsoil and 85% of the midsoil sampled in 1999 had pH values < 5.0, with 15% of these soils having a pH value of < 4.0. Liming recommendations were provided to growers, and after resampling seven years later an overall increase in soil pH was measured, with approximately 15% less sites recording a pH < 5.0 of of soils and no samples found to be < pH 4.0.
Grain yield in limed paddocks was found to be on average 6-7% higher than in unlimed paddocks, though recorded significantly higher yield in drier seasons.
Source: Stephen Carr1, David York1, Joel Andrew1 *& Chris Gazey2 (1Aglime of Australia, Precision SoilTech; 2Department of Agriculture and Food Western Australia). Avon Catchment Council SI002 Case Study 2006
Case study 2
Long term lessons from liming soil
Long term trials have shown continuous cropping under a cereal legume rotation with district practice application of fertiliser N and retention of stubble caused a decrease in soil pH of up to 1.6 units over 14 years. Reduced N inputs can lessen this impact (as can stubble removal) but also decreases yield.
At Wagga, the application of lime in combination with phosphorous (P) increased grain yields by almost 100%, whilst stocking rates increased by 25% after six years. Soil pH initially increased from pH 4.0 to 5.5 after application of 3.7 t/ha lime, but subsequently decreased back to 5.0 over the next six years.
- High initial lime rates will improve soil pH more rapidly and allow excess lime to move deeper into the profile addressing subsoil acidification.
- Maintenance lime is required to maintain changes in soil pH.
- Liming may increase N leaching.
- P application is more efficient.
- Excessive N application and leaching of nitrate is likely to accelerate the decline in soil pH.
Source: MASTER Trial, Wagga Wagga; Tarlee long term rotation trial; Rutherglen SR1
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